In 1990, a whopping 23,000 people were murdered in America. But when New York City announced Thursday that its murder rate was on track to reach a historic low, it was just the latest reminder of a nationwide plummet in murders over the last two decades.

And while the trend has been widespread — murders were down all the way to 14,000 nationwide last year from the 23,000 mark in 1990 — the improvement has been especially stunning in the Big Apple, criminologists say.

“New York has had the largest and most consistent decline in serious crime of any city in the country,” said David Kennedy, a professor at the John Jay College of Criminal Justice and director of the Center for Crime Prevention and Control. “The scale and the trajectory and the consistency is unique nationally.”

New York police boasted of their latest improvements Thursday, heralding a 27 percent drop in murders so far this year that, if maintained, would see the country’s largest city suffer less than one murder a day on average in 2013.

In 1990, the city could claim nearly 10 percent of all U.S. murderes. That year, the city’s most violent, 2,245 people were murdered. In 2012, the city reported 419 murders, just 3 percent of U.S. murders.

The city now has among the lowest murders rates — defined as murders per 100,000 people — of large cities. In 2012, New York City had a murder rate of about 5.0, below Los Angeles’ rate of 7.8, and less than a third of Chicago’s rate, where murders spiked before showing signs of slowing this year.

Across the country, murder rates fell precipitously in the 1990s at the tail end of the crack cocaine-induced drug wars. The figures leveled out in the 2000s, until 2009, when murder rates fell again over the next two years. The drop came as a surprise to law enforcement officials, who expected the economic recession to have a negative effect on crime, according to Alfred Blumstein, a criminologist at Carnegie Mellon University and author of The Crime Drop in America.

In New York, by contrast, homicides have dropped in all but four years since 2000.

The reasons behind New York’s exceptional drop are often debated — outgoing Mayor Michael Bloomberg has held up the controversial police tactic of stop-and-frisk as a major driver despite criticism that it amounts to little more than racial profiling — but Kennedy says innovative policing in general has left its mark. More recently, for example, New York police began targeting gang violence by closely monitoring the social and family circles of criminals, and by paying closer mind to social media use by gang members.

Outside the reach of law enforcement, rising incomes and real estate have transformed entire urban neighborhoods in New York, said Eugene O’Donnell, a former city cop who lectures at John Jay College.

“We kept saying how low can you go, and they’re still going lower,” O’Donnell said. “Increasingly, we’re seeing that New York City stands alone. While law enforcement certainly has played a role, there other dynamics that are going on in the city that put it in a class by itself.”